#include <fstream>
#include <vector>
#include <stack>
#define NMAX 100005

using namespace std;

ifstream in("ctc.in");
ofstream out("ctc.out");

vector <int> adj[NMAX];
vector <int> inv_adj[NMAX];
stack <int> st;
vector <int> cmp_cnx[NMAX];
bool cmp[NMAX];
bool viz[NMAX];

void dfs1(int node)
{
    viz[node] = 1;

    for (int i = 0; i < adj[node].size(); ++i)
    {
        int vecin = adj[node][i];
        if (viz[vecin] == 0)
            dfs1(vecin);
    }
    st.push(node);
}

void dfs2(int node, int cnt)
{
    cmp_cnx[cnt].push_back(node);
    cmp[node] = 1;

    for (int i = 0; i < inv_adj[node].size(); ++i)
    {
        int vecin = inv_adj[node][i];
        if (cmp[vecin] == 0)
            dfs2(vecin, cnt);
    }
}

int main()
{
    int n, m, i, j, a, b, cnt = 0;
    in >> n >> m;
    for (i = 1; i <= m; ++i)
    {
        in >> a >> b;
        adj[a].push_back(b);
        inv_adj[b].push_back(a);
    }

    for (i = 1; i <= n; ++i)
    {
        if (viz[i] == 0)
            dfs1(i);
    }

    while (!st.empty())
    {
        int node = st.top();
        st.pop();
        if (cmp[node] == 0)
        {
            ++cnt;
            dfs2(node, cnt);
        }
    }

    out << cnt << '\n';
    for (i = 1; i <= cnt; ++i)
    {
        for (j = 0; j < cmp_cnx[i].size(); ++j)
            out << cmp_cnx[i][j] << " ";
        out << '\n';
    }
    return 0;
}